Dimethyl carbonate, production

The conventional electrochemical reduction of carbon dioxide tends to give formic acid as the major product, which can be obtained with a 90% current efficiency using, for example, indium, tin, or mercury cathodes. Being able to convert CO2 initially to formates or formaldehyde is in itself significant. In our direct oxidation liquid feed fuel cell, varied oxygenates such as formaldehyde, formic acid and methyl formate, dimethoxymethane, trimethoxymethane, trioxane, and dimethyl carbonate are all useful fuels. At the same time, they can also be readily reduced further to methyl alcohol by varied chemical or enzymatic processes. 

Other approaches have explored the reaction of amines with dimethyl carbonate or its precursors (28). A reaction scheme for the production of polymeric MDI is as follows ... 

As in the case of the chloroformates, most of the carbonate production is used captively and production figures are not available. However, from pubHshed data, the 1991 price (fob works) of commercial carbonates was 3.08/kg for both dimethyl (DMC), dmms, tmcHoad and diethyl (DEC), tankwagon (89). 

Dimethyl carbonate [616-38-6] and dimethyl oxalate [553-90-2] are both obtained from carbon monoxide, oxygen, and methanol at 363 K and 10 MPa (100 atm) or less. The choice of catalyst is critical cuprous chloride (66) gives the carbonate (eq. 20) a palladium chloride—copper chloride mixture (67,68) gives the oxalate, (eq. 21). Anhydrous conditions should be maintained by removing product water to minimize the formation of by-product carbon dioxide. 

Oxygenates and Chemicals A whole host of oxygenated products, i.e., fuels, fuel additives, and chemicals, can be produced from synthesis gas. These include such produc ts as methanol, ethylene, isobutanol, dimethyl ether, dimethyl carbonate, and many other hydrocarbons and oxyhydrocarbons. Typical oxygenate-producing reactions are ... 

Dimethyl carbonate is available from Aldrich Chemical Company, Inc. The checkers dried the tetrahydrofuran Immediately before use by distillation from the sodium ketyl of benzophenone under a nitrogen atmosphere. The submitters purchased sodium hydride (50% oil dispersion) from Alfa Products, Morton/Thiokol, Inc. The checkers used 12.24 g of a 50% dispersion of sodium hydride in mineral oil obtained from the same supplier. The dispersion was washed with three portions of pentane to remove the mineral oil and the remaining sodium hydride was allowed to dry under nitrogen. 

A solution of 0.1 mol of each of thiophene-2-carboxaldehyde and 1,2-dimethyl-1,4,5,6-tetrahydropyrimidine in dimethyl carbonate (0.2 mol) is held at 27°C for 48 hours. The reaction mixture is then stripped to give a 65% yield of product as the free base. 

Dimethyl carbonate (DMC) is a colorless liquid with a pleasant odor. It is soluble in most organic solvents but insoluble in water. The classical synthesis of DMC is the reaction of methanol with phosgene. Because phosgene is toxic, a non-phosgene-route may be preferred. The new route reacts methanol with urea over a tin catalyst. However, the yield is low. Using electron donor solvents such as trimethylene glycol dimethyl ether and continually distilling off the product increases the yield. ... 

What product would you expect to obtain from Grignard reaction of an excess of phenylmagnesium bromide with dimethyl carbonate, CH30C02CH3 ... 

Both new catalysts and new processes need to be developed for a complete exploitation of the potential of CO2 use [41]. The key motivation to producing chemicals from CO2 is that CO2 can lead to totally new polymeric materials and also new routes to existing chemical intermediates and products could be more efficient and economical than current methods. As a case in point, the conventional method for methanol production is based on fossil feedstock and the production of dimethyl carbonate (DMC) involves the use of toxic phosgene or CO. A proposed alternative production process involves the use of CO2 as a raw material (Figure 7.1)... 

Today most dimethyl carbonate is made by methanol carbonylation (Equation 3.2) using a copper chloride catalyst with a very long life. This process produces pure dimethyl carbonate, which is not now classified as harmful, and water as a by-product. 

One example of a new class of compound in this area is dioctyl carbonate (1, Table 4.9). The product is synthesized by the trans-esterification reaction of octa-nol and dimethyl carbonate in the presence of alkali catalyst (Fig. 4.20). Dioctyl carbonate (Cetiol CC) is a dry emollient with excellent dermatological compatibility and a comprehensive and convincing performance profile for various appli-... 

The oxidative carbonylation of alcohols and phenols to carbonates can be catalyzed by palladium or copper species [154-213]. This reaction is of particular practical importance, since it can be developed into an industrial process for the phosgene-free synthesis of dimethyl carbonate (DMC) and diphenyl carbonate (DPC), which are important industrial intermediates for the production of polycarbonates. Moreover, DMC can be used as an eco-friendly methylation and carbonylation agent [214,215]. The industrial production of DMC by oxidative carbonylation of methanol has been achieved by Enichem [216] and Ube [217]. 

Comparison of the configuration of the stannane with the prodncts of reaction reveals that primary alkyl halides that are not benzyhc or a to a carbonyl react with inversion at the lithium-bearing carbon atom. In the piperidine series, the best data are for the 3-phenylpropyl compound, which was shown to be >99 1 er. In the pyrrolidine series, the er of the analogous compound indicates 21-22% retention and 78-79% inversion of configuration. Activated alkyl halides such as benzyl bromide and teri-butyl bromoacetate afford racemic adducts. In both the pyrrolidine and piperidine series, most carbonyl electrophiles (i.e. carbon dioxide, dimethyl carbonate, methyl chloroformate, pivaloyl chloride, cyclohexanone, acetone and benzaldehyde) react with virtually complete retention of configuration at the lithium-bearing carbon atom. The only exceptions are benzophenone, which affords racemic adduct, and pivaloyl chloride, which shows some inversion. The inversion observed with pivaloyl chloride may be due to partial racemization of the ketone product during work-up. 

This method of transesterification is of high technical interest. Particularly the reaction of bisphenol A with diphenyl carbonate is a preferred phosgene-free process because biphenyl carbonate can be obtained directly from phenol and dimethyl carbonate.The latter is an industrial product made from CO and methanol. 

The reaction of dimethyl carbonate with synthesis gas requires a cobalt-iodide catalyst and operating conditions of 180 C and 4000 psig. The acetaldehyde rate approaches 30 M/hr with selectivities greater than 85%. The productivities are much better than with methanol however, recycle of the CO and methanol back to dimethyl carbonate is very difficult ... 

Fig. 4.3 Data of Raman spectroscopy (He-Ne laser, A,=632,8 nm) for the following samples 1 - polyvinyl chloride-polyvinylidene chloride composition after chemical dehydrochlorination (80°C, KOH in dimethyl sulfoxide -propan-2-ol 1 1, w/w) 2 - chemically dehydrochlorinated polymer carbonized in CO at 350°C 3 - carbonized product activated in CO at 950°C...

The reaction exhibits an induction period. Comparison of different catalyst precursors shows that the behaviour of Pd/C is similar to that of PdCl2 (Table 2). Examination of the medium at the first stages of the reaction indicates in both cases the formation of dimethyl carbonate. This product is known to be formed by the reaction of CO and MeOH in the presence of 02 and PdCl2 (ref. 13). 

Aresta and Quaranta studied the reactivity of alkylammonium N-alkylcarbamates (RNH3)02CNHR towards a different acylating substrate, such as dimethyl carbonate (DMC) [62a, b]. Carbamate salts (RNH3)02CNHR (R = benzyl, allyl, cyclohexyl), prepared in situ from aliphatic primary amines and C02, reacted with DMC to afford N-alkyl methylcarbamates (Equation 6.6). The reaction requires mild conditions (343-363 K 0.1 MPa C02 pressure) and can be carried out in DMC used as solvent and reagent. At 363 K, carbamate esters were obtained in satisfactory yield (45-92%) with high selectivity, as side products such as ureas, N,N-dialkylcarbamate esters, and alkylated amines were formed in very small amounts. 

The lithiated species 120, also obtainable by metal exchange of the tin analogues, reacts with electrophiles such as methyl halides, benzaldehyde, or dimethyl carbonate to give products such as 123-125, respectively. ... 

The properties of dimethyl carbonate, (MeO)2CO, as an ambident electrophile have been investigated by analysis of the products of its reaction with various nucleophiles having different hard-soft character. Results were in good agreement with the Hard-Soft Acid-Base theory, hard nucleophiles attacking the hard C=0 group and soft nucleophiles the soft Me group (Scheme ll).37... 

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